#428 uncovered .defaults that URL-like classes use overwrite.

The API itself is like this:

{Git,Svn,Hg}URL have a __post_init__ that iterate over .matches.

1. It doesn't stop when it finds a match
2. So other matchers with .defaults overwrite
3. There's no weighting / preference of matches over another

My tasks: I will need to figure out the above, and write tests and doctest examples to "shake out" similar usage-type cases like this that aren't catchable in a vacuum